Sulfuric acid concentration sensor for lead storage battery

Abstract

A sulfuric acid concentration sensor for a lead storage battery comprising a quartz resonator changing its characteristic frequency in a manner of single-valued function according to the change of sulfuric acid concentration and an oscillation circuit (20) oscillating the quartz resonator, the quartz resonator is immersed in an electrolyte (6) so as to be oscillated, and a characteristic frequency of the quartz resonator at this moment is obtained so as to determine the sulfuric acid concentration. The sensor of this invention is compact in its size, simple in its structure and cheap in its cost, so that it can be applied to a lead storage battery for automobile.

What is claimed is: 
     
       1. In a sensor for detecting a sulfuric acid concentration of electrolyte for a lead storage battery, a sulfuric acid concentration sensor for the lead storage battery comprising: a quartz resonator changing its characteristic frequency in an approximately linear relationship according to a change of sulfuric acid concentration, and an oscillation circuit coupled to and oscillating the quartz resonator, the quartz resonator being immersed in an electrolyte such that a characteristic frequency of the quartz resonator during oscillation is obtained so as to determine the sulfuric acid concentration;   wherein the quartz resonator further comprises:   electrodes installed on both surfaces of the quartz resonator plate respectively, each electrode being electrically coupled to the oscillation circuit, the quartz resonator plate being so installed that only one side surface of the plate contacts an electrolyte, and an electrode at the side contacting with the electrolyte being grounded through a condenser in respect of alternating current.   
     
     
       2. A sulfuric acid concentration sensor for a lead storage battery as set forth in claim 1, in which the quartz resonator plate forming the quartz resonator is installed in an inclined position or a perpendicular position. 
     
     
       3. A sulfuric acid concentration sensor for a lead storage battery as set forth in claim 1, wherein the quartz resonator is formed with a quartz resonator plate, the quartz resonator plate being positioned at a liquid surface lower limit line of the electrolyte to function as a level gauge. 
     
     
       4. A sulfuric acid concentration sensor for a lead storage battery as set forth in claim 1, in which the quartz resonator and the oscillation circuit are installed in a port plug of the lead storage battery, the port plug has a immersion portion to be immersed in the electrolyte, the immersion portion comprises a cylindrical portion having an opening, the quartz resonator is so installed as to close said opening to seal an inside of said cylindrical portion, and the oscillation circuit is installed in a cover portion. 
     
     
       5. A sulfuric acid concentration sensor for a lead storage battery as set forth in claim 1, in which the quartz resonator and the oscillation circuit are installed in a port plug of the lead storage battery, the port plug has a immersion portion to be immersed in the electrolyte, the immersion portion comprises a cylindrical portion having an opening, the quartz resonator and the oscillation circuit are installed on a single substrate, and the single substrate is so installed that the oscillation circuit is located in said cylindrical portion and closes said opening so as to seal an inside of said cylindrical portion. 
     
     
       6. A sulfuric acid concentration sensor for a lead storage battery as set forth in claim 1, in which a power of the oscillation circuit is supplied from a lead storage battery a sulfuric acid concentration of which is to be measured. 
     
     
       7. In a sensor for detecting a sulfuric acid concentration of electrolyte for a lead storage battery, a sulfuric acid concentration sensor for the lead storage battery comprising: a quartz resonator changing its characteristic frequency in an approximately linear relationship according to a change of sulfuric acid concentration, and an oscillation circuit coupled to and oscillating the quartz resonator, the quartz resonator being immersed in an electrolyte such that a characteristic frequency of the quartz resonator during oscillation is obtained so as to determine the sulfuric acid concentration; and   wherein the quartz resonator has a temperature coefficient for compensating a temperature coefficient of sulfuric acid.   
     
     
       8. In a sensor for detecting a sulfuric acid concentration of electrolyte for a lead storage battery, a sulfuric acid concentration sensor for the lead storage battery comprising: a quartz resonator changing its characteristic frequency in an approximately linear relationship according to a change of sulfuric acid concentration, and an oscillation circuit coupled to and oscillating the quartz resonator, the quartz resonator being immersed in an electrolyte such that a characteristic frequency of the quartz resonator during oscillation is obtained so as to determine the sulfuric acid concentration; and   wherein lead dioxide is plated on a surface of the quartz resonator at least on a side contacting the electrolyte.   
     
     
       9. In a sensor for detecting a sulfuric acid concentration of electrolyte for a lead storage battery, a sulfuric acid concentration sensor for the lead storage battery comprising: a quartz resonator changing its characteristic frequency in an approximately linear relationship according to a change of sulfuric acid concentration, and an oscillation circuit coupled to and oscillating the quartz resonator, the quartz resonator being immersed in an electrolyte such that a characteristic frequency of the quartz resonator during oscillation is obtained so as to determine the sulfuric acid concentration;   wherein the quartz resonator and the oscillation circuit are installed in a port plug of the lead storage battery, the port plug has a immersion portion to be immersed in the electrolyte, the immersion portion comprises a cylindrical portion having an opening, the quartz resonator is so installed as to close said opening to seal an inside of said cylindrical portion, and the oscillation circuit is installed in a cover portion; and   wherein the immersion portion is made of a material having a coefficient of linear expansion as close as possible to that of a quartz resonator plate forming the quartz resonator.   
     
     
       10. In a sensor for detecting a sulfuric acid concentration of electrolyte for a lead storage battery, a sulfuric acid concentration sensor for the lead storage battery comprising: a quartz resonator changing its characteristic frequency in an approximately linear relationship according to a change of sulfuric acid concentration, and an oscillation circuit coupled to and oscillating the quartz resonator, the quartz resonator being immersed in an electrolyte such that a characteristic frequency of the quartz resonator during oscillation is obtained so as to determine the sulfuric acid concentration;   wherein the quartz resonator and the oscillation circuit are installed in a port plug of the lead storage battery, the port plug has a immersion portion to be immersed in the electrolyte, the immersion portion comprises a cylindrical portion having an opening, the quartz resonator and the oscillation circuit are installed on a single substrate, and the single substrate is so installed that the oscillation circuit is located in said cylindrical portion and closes said opening so as to seal an inside of said cylindrical portion; and   wherein the substrate is made of a material having a coefficient of linear expansion as close to the quartz resonator plate forming the quartz resonator as possible.